Abstract: For 300 m-high earth core rockfill dams, the creep characteristics of dam body have the vital significance in prediction of long-term deformation and settlement after dam construction. Meanwhile they are also very important to be used to evaluate whether or not the impervious core wall can match the long-term deformation of dams and keep on normal operation. Based on Shuangjiangkou Dam (314 m high, earth core rockfill dam), rockfill materials are tested by using a large high-pressure triaxial apparatus to study the creep characteristics. The results show that under multi-stage loading and single-stage loading, the difference of creep curves from the two tests decreases with the development of time when the tests have the same final stress state. And finally, the creep curves tend to converge. Using the empirical model for creep, the relevant parameters are obtained from the test data. The creep characteristics of 300 m-high earth core rockfill dam are analyzed by using the 3D finite element method. The numerical analysis shows that the creep velocity has a distinct influence on the settlement after dam construction. Compared with that of the actual creep conditions in dam body, the creep velocity in tests is much faster, so it’s necessary to make inverse analysis according to the built dams, which can provide an available method to amend the creep velocity.